The present invention relates generally to router bits for routing predetermined configurations in a workpiece and, more particularly, to a router bit which has two pairs of cutter elements for smoothly and precisely cutting the predetermined configurations while leaving a smooth surface.
Router bits have long been used for cutting various configurations, such as a bevel or straight-sided groove, in workpieces composed of wood or other appropriate materials. Router bits have also been used to cut more complicated configurations, such as those involved in forming a raised panel, as shown in Witt U.S. Pat. No. 4,844,1350. However, these complicated configurations typically require that cuts be made in a workpiece so as to form cut surfaces which have a varied angular and/or curved profile, with the profile extending both parallel to the major surface of the workpiece and also perpendicular to such surface. The "ooge" or S-shaped pattern is typical of such configurations formed in, among other components, raised panels.
Previous router bits have typically not been able to cut such complicated configurations so as to leave smooth and precisely formed cut surfaces. Moreover, when routing a raised panel edge on all four edges of a wooden panel, routing operations on two of the edges will typically involve the cutting of end grain. It has long been recognized that cutting of end grain presents particular challenges in that wood fibers in this orientation have the greatest ability to resist cutting, yet are likely to splinter, and the cutting of end grain is therefore ordinarily difficult at best.
Router bits are ordinarily mounted in a routing machine which has a rotational speed of approximately 8,000 to 24,000 rpm and a power most often in the range of approximately 1 to 3.25 horsepower. Router bits have relatively low mass, and the typically low horsepower of routing machines results in the router bits usually being driven with a relatively low torque.
The smooth cutting of complex configurations with shaper cutters, which are larger than router bits and ordinarily are driven with significantly higher horsepower and torque, has been assisted by the "2+2" Raised Panel Cutters of the assignee of the present application. These shaper cutters employ a pair of cutter elements which are essentially dedicated to cutting the portion of the raised panel configuration which extends along the axis of the cutter, or perpendicular to the major surface of the workpiece, and these cutters are mounted with a negative shear angle. However, the use of such an arrangement can increase the cutting resistance met by the cutter and has not been known to be used in router bits which are driven at a lower horsepower and lower torque. The less powerful routing machines, which are used by hobbyist woodworkers and small scale woodworking shops, are usually much less expensive than shaper cutters.
Consequently, a need therefore exists for a router bit which is capable of accurately cutting complicated configurations in a workpiece, while leaving smooth cut surfaces.